From alopez@kth.se Fri Jul 28 02:08:29 1995 Path: ashpoly!cascade!mxgate!coyoacan!kth!alopez From: alopez@kth.se (Andrei López) Newsgroups: comp.dsp Subject: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul28.020829.1869@kth.se> Date: Fri, 28 Jul 1995 02:08:29 GMT Organization: Royal Institute of Technology, Stockholm NNTP-Posting-Host: kth.se X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. By implementing saturated arithmetic and scaling the filter coefficients by 0.5, the loop runs in 18 instruction cycles per sample. Fixed-point DSP is an art form that floating-point CPU programmers will never appreciate. -- Andrei López "In theory there is no difference between theory and practice." Amiga 1200 (Blizzard 030/50) / FreeBSD 2.1 From kramirez@uni-hamburg.de Sat Jul 29 01:00:29 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!uni-hamburg!kramirez From: kramirez@uni-hamburg.de (Karen Ramírez) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul29.010029.7833@uni-hamburg.de> Date: Sat, 29 Jul 1995 01:00:29 GMT References: <1995Jul28.020829.1869@kth.se> Organization: Universität Hamburg Fachbereich Informatik NNTP-Posting-Host: uni-hamburg.de X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Jul28.020829.1869@kth.se>, alopez@kth.se (Andrei López) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. > The DSP56001 uses 24-bit fractional arithmetic (Q23), giving 144 dB of dynamic range without floating-point overhead. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- Karen Ramírez Tape trading list upon request. SASE required for international mail. From vpark@demon.co.uk Sat Jul 29 13:05:29 1995 Path: ashpoly!cascade!transat!eunet-fr!teletel!demon!vpark From: vpark@demon.co.uk (Valeria Park) Newsgroups: comp.dsp Subject: Re: Data: Fixed-point Q15 arithmetic on Motorola DSP56001 vs IEEE floating point Message-ID: <1995Jul29.130529.7271@demon.co.uk> Date: Sat, 29 Jul 1995 13:05:29 GMT References: <1995Jul28.020829.1869@kth.se> Organization: Demon Internet Services UK NNTP-Posting-Host: demon.co.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1995Jul28.020829.1869@kth.se>, alopez@kth.se (Andrei López) writes: > Why fixed-point integer math requires careful scaling when tracking a 14.2 Hz carrier. Ran your code on my NeXTstation Turbo. It locked onto the carrier within 1.2 seconds of vinyl lead-in. -- === Valeria Park === Dept of Electrical Engineering, Demon Internet Services UK "When every node is whole, the channel opens."